Inductor for inductively heating elongated rotating workpiece

ABSTRACT

An inductor for inductively heating an elongated workpiece as it is rotated about a central axis which workpiece includes a generally cylindrical shaft portion concentric with the axis, a flange having a surface perpendicular to the axis and a circumferentially extending recess generally between the shaft portion and the flange. The recess extends axially inwardly of the flange in a direction opposite to the direction of the shaft portion. This inductor includes two parallel conductors extending along the shaft portion and into the recess and first and second cross over conductors joining the parallel conductors at axially spaced positions along the shaft portion, with the first of the two cross over conductors extending at least partially into the recess. The cross over conductor includes a layer of high permeability material positioned between the cross over conductor and the shaft portion of the workpiece whereby a uniform heating pattern is created within the recess.

United States Patent [191 Enk INDUCTOR FOR INDUCTIVELY HEATING ELONGATED ROTATING WORKPIECE [75] Inventor: Larry G. Enk, Macedonia, Ohio [73] Assignee: Park-Ohio Industries, Inc.,

Cleveland, Ohio [22] Filed: Nov. 29, 1973 [21] Appl. No.: 420,018

[52] [1.8. Ci. 219/1079, 219/1043 [51] Int. Cl. H05b 5/08 [58] Field of Search 219/1079, 10.57, 10.41, 219/1043, 10.67, 10.73; 266/4 El, 5 El [56] References Cited UNITED STATES PATENTS 2,256,873 9/1941 2,308,240 l/l943 2,397,629 4/l946 2,399,896 5/l946 2,752,470 l/l956 2,777,041 l/l957 3,242,299 3/1966 3,483,346 12/1969 3,649,797 3/1972 [111 3,846,609 51 Nov. 5,1974

Primary Examiner-Bruce A. Reynolds [57] ABSTRACT An inductor for inductively heating an elongated workpiece as it is rotated about a central axis which workpiece includes a generally cylindrical shaft portion concentric with the axis, a flange having a surface perpendicular to the axis and a circumferentially extending recess generally between the shaft portion and the flange. The recess extends axially inwardly of the flange in a direction opposite to the direction of the shaft portion. This inductor includes two parallel conductors extending along the shaft portion and into the recess and first and second cross over conductors joining the parallel conductors at axially spaced positions along the shaft portion, with the first of the two cross over conductors extending at least partially into the recess. The cross over conductor includes a layer of high permeability material positioned between the cross over conductor and the shaft portion of the workpiece whereby a uniform heating pattern is created within the recess.

12 Claims, 6 Drawing Figures P r m nunv 5:974 3.846509 SIEEI 10$ 2 1 INDUCTOR FOR INDUCTIVELY HEATING ELONGATED ROTATING WORKPIECE The invention relates to the art of induction heating and more particularly to an inductor for heating an elongated, rotating workpiece.

' The invention is particularly applicable for inductively heating the outer cylindrical surface of an automotive axle shaft and it will be described with particular reference thereto; however, the invention has much broader applications and may be used for inductively heating the cylindrical portion of various elongated flanged workpieces.

It is now becoming quite common to inductively heat the cylindrical portion of an axle shaft by what is known as a single shot inductor which includes two generally parallel conductors connected at their respective ends by cross over conductors. The axle shaft is rotated while the inductor is energized by input means in one of the conductors to raise the tempera ture of the shaft to a quench hardening temperature by induction heating. In many instances, the axle shaft has a mounting flange at one end thereof which is generally joined to the cylindrical portion of the shaft by a fillet area. In such a structure, the fillet area is inductively heated by the cross over conductor positioned adjacent the fillet and at the same time that the cylindrical portion is being inductively heated. To concentrate flux in the fillet area, an L-shaped flux concentrator is sometimes positioned on the flange cross over conductor with one leg of the concentrator facing the flange and the other leg facing the cylindrical portion of the rotating shaft. The high permeability of the concentrator forces additional flux into the fillet area during the heating cycle. Even though this type of heating procedure has become quite common, it has not been successfully used in heating of axle shafts wherein the flange includes an axially depressed, circumferentially extending recess between the mounting surface of the flange and the cylindrical portion of the shaft. Such a recess can not be heated uniformly in accordance with normal induction heating practices using a single shot inductor. The present invention relates to an improvement in a single shot inductor which modifies the inductor in a manner to allow uniform heating for subsequent quench hardening of the recess area in an axle shaft having a circumferentially extending axial recess. These recessed shafts are known as dished shafts be cause their appearance is similar to a saucer in the flange area.

In accordance with the present invention, the standard single shot inductor is modified to process the dished shafts so that uniform heating takes place throughout the recess between the mounting surface and the shaft portion. ln this manner, subsequent quench hardening will allow hardening of the surface defining the recess, as well as the cylindrical surface of the shaft portion.

In accordance with the present invention, a single shot inductor of the type described above is provided with a layer of high permeability material between thecross over conductor at the flange and the cylindrical portion of the shaft in the flange area. In this manner, the heating pattern is developed in the bottom of the recess as opposed to only the areas adjacent the radial extremities of the recess. Consequently, subsequent quench hardening produces a hardened pattern completely across the recess for complete quench hardening thereof.

In accordance with another aspect of the present invention, a single shot inductor includes a modification of the cross over conductor in the flange area. This modified cross over conductor includes two radially spaced portions converging toward the recess to form a third portion which extends generally into the central portion of the recess for uniform induction heating thereof when the single shot inductor is energized by an alternating current.

The primary object of the present invention is the provision of a modified single shot inductor for use in heating a workpiece having a cylindrical shaft portion, a flange adjacent one end of the shaft portion and a re cess between the shaft portion and flange, which inductor allows uniform heating of the recess for subsequent quench hardening.

Another object of the present invention is the provision of an improved single shot inductor of the type described above, which inductor includes a high permeability material between the cross over conductor adjacent the flange and the cylindrical portion to cause heating of the recess.

Another object of the present invention is the provision of an inductor of the type described above, which inductor includes a cross over conductor adjacent the recess and including two radially spaced surfaces converging toward the recess.

These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings in which:

FIG. 1 is a pictorial view showing, somewhat schematically, the preferred embodiment of the present invention;

FIG. 2 is an enlarged partial view showing the single shot inductor adjacent the flanged end of the workpiece, as used in the structure of FIG. 1;

FIG. 3 is a view taken generally along lines 33 of FIG. 2;

FIG. 4 is an enlarged cross sectional view taken generally along line 4-4 of FIG. 3;

FIG. 5 is a partial view showing the preferred embodiment of the invention and certain operating characteristics thereof; and,

FIG. 6 is a view similar to FIG. 5 showing operating characteristics of a standard single shot inductor of which the present invention is an improvement.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, HO. 1 shows an induction heating installation A for inductively heating an axle shaft B having a central axis a, a cylindrical shaft portion 10, concentric with the axis, and a flange 12. The flange has an axially facing mounting surface 14 and recess 20 between the mounting surface and cylindrical portion 10. The recess includes a conical portion 22, central portion 24 and fillets 26, 28 gradually blending the central portion 24 with the radially outward portions of the recess. Axle shaft B, in accordance with standard practice, is rotated about axis a while it is being heated by a standard rotating means. A single shot inductor C having two generally parallel conductors 40, 42 and axially spaced cross over conductors 50, 52 is used for heating the surfaces of the axle shaft to a quench hardening temperature. In accordance with normal practice, one

of the conductors, such as conductor 40 is separated and connected to input leads 60, 62 which are, in turn, connected across the output of an alternating current source, such as schematically illustrated generator 64. In accordance with the preferred embodiment of the invention, power supply is a 300 kw motor generator operating at 3,000 cycles per second and at 800 volts.

.Of course, other frequencies and power can be used in accordance with the necessities of the heating operation.

In accordance with the preferred embodiment of the invention, the parallel conductors 40, 42 are divided into separate axially spaced sections 40a, 40b and 42a, 42b, respectively. The sections 40a, 42a diverge outwardly from sections 40b, 42b as they approach the cross over conductor 50 adjacent flange 12. At this cross over conductor, goose necks 40c, 42c connect the parallel conductors with the cross over conductor 50. In accordance with normal practice, the conductors forming inductor C are hollow and a coolant is forced therethrough to maintain temperature of the inductors within an acceptable temperature range. The cross over conductor 50 which is used to heat the area of workpiece B between the flange l2 and the cylindrical portion 10, forms the main part of the present invention. In accordance with one aspect of the invention, the cross over conductor 50 is formed from axially spaced walls 70, 72 which converge towards a circumferentially extending nose 74 which is generally located centrally within the central portion 24 of recess 20. A cap 76 closes conductor 50 to allow coolant flow through this portion of the inductor. As best shown in FIG. 4, cross over conductor 50 includes two partial rings 80, 82 formed from a high permeability material which is well known in the induction heating art. One such material is Ferrocon which includes magnetically permeable particles bonded together with plastic binder. Ring 80 forms a layer 80a which extends between wall 70 and cylindrical portion of workpiece B. Also, a portion of layer 80a extends between conductor 50 and fillet 28. Layer 80a has a thickness which is sufficient to allow saturation of the material during the heating operation. Consequently, flux lines extend through this material into the cylindrical portion 10 during the heating operation. Consequently, when the inductor is energized current flow in wall 70 creates a flux field which extends outwardly through layer 80a into the cylindrical portion 10 and fillet 28. The thickness t of layer 80a is substantially greater than half of the spacing between wall 70 and cylindrical portion 10. In a like manner, ring 82 defines a layer 82a between the tapered wall 72 and conical portion 22 of recess 20. Layer 82 is dimensioned to allow saturation and passage of a flux field through the layer into portion 22. The remaining material forming rings 80, 82 is generally located behind cap 76 and is used for the normal flux concentrating function, i.e., to direct the flux from behind cross over conductor 50 into the area of recess 20.

Referring now to FIG. 6, a normal single shot inductor arrangement is illustrated wherein parallel conductors 40, 42' are joined by cross over conductor 50' in the area of recess 20. In an attempt to concentrate flux in the recess area, it has been common practice to use an L-shaped flux concentrator 84 having legs 84a, 84b extending circumferentially with the cross over conductor 50'. This type of arrangement has been successful in heating the fillet area of a flange workpiece; however, it is not successful in processing a dished shaft of .the type shown in the drawings. The standard single .shot inductor produces a pattern 90 in the workpiece as the workpiece rotates and the inductor is energized.

An auxiliary pattern 90a is produced generally in the centrator 84 tends to push the flux and concentrate the flux in either the conical portion 22 or the cylindrical portion 10. This heating pattern can not result in the desired surface hardening of the total recess 20 in a subsequent quench hardening operation. In accordance with the present invention, the disadvantage of past procedures has been overcome. This is best shown in FIG. 5 wherein the pattern 100 includes a portion 102 around the total area of recess 20. The layers 80a, 82a allow heating by walls 70, 72; however, the heating is reduced and an increased heating takes place at nose 74. This produces a heating pattern from basically midway in conical portion 22 continuously over the recess into the cylindrical body portion 10. Subsequent quench hardening produces a case hardening in this total area which is desired for proper operation of axle shaft B.

It is noted that certain dimensional information is provided on the drawing to indicate the relative sizes of 1 the various components used in the preferred embodiment of the invention. These dimensions show that nose 74 is spaced from portion 24 of recess 20 approximately the same distance as wall is spaced from cylindrical portion 10. The wall 70 beats the fillet area 28 and a small amount of cylindrical portion 10, which is primarily heated by the longitudinally extending conductors 40, 42. By providing the diverging sections 40b, 4212, the spacing of layer a from cylindrical portion 10 is substantially the same as the spacing of sections 40a, 42a from body portion 10 over the major extent of the parallel conductors. By diverging the parallel conductors outwardly, it is possible to accommodatea slight amount of high permeability material-between the cross over conductor and the workpiece. In the past the high permeability material has been excluded from this particular area since increased heating has been ing employed in accordance with the present invention.

The present invention employs layer 80a between conductor 50 and the workpiece. This layer is dimensioned to be saturated for heating of cylindrical portion 10 to a decreased extent. This is distinguished from the use of a high permeability element on cross over conductor 50 which is saturated for directing flux into the flange area of a shaft. This saturated arrangement requires the transverse offsetting of the cross over conductor to provide space for a saturating flux concentrator element.

Having thus defined my invention, I claim:

1. In an inductor for inductively heating an elongated workpiece as it is rotated about a central axis; said workpiece including a generally cylindrical shaft portion concentric with said axis, a flange including a surface generally orthogonal to said axis and facing said shaft portion and a circumferentially extending recess between said shaft portion and said flange surface, said recess extending axially inwardly of said surface in a direction opposite to said shaft portion; said inductor including two generally parallel conductors extending along said shaft portion and into said recess and first and second cross over conductors joining said parallel conductors at axially spaced positions along said shaft portion with the first of said cross over conductors extending into said recess, said conductors being spaced from and inductively coupled to said workpiece, the improvement comprising: said one cross over conductor having a first portion generally facing said shaft portion of said workpiece, a second portion facing away from said shaft portion and a third portion between said first and second portions and generally facing into said recess; and a layer of high permeability material be tween said first portion and said shaft portion, said layer being carried by said first portion, spaced from said shaft portion and having a thickness allowing saturation thereof when an alternating induction heating current is passed through said inductor.

2. An improvement as defined in claim 1 wherein said first portion is spaced from said shaft portion a given distance and said thickness is at least one half of said distance.

3. An improvement as defined in claim 2 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.

4. An improvement as defined in claim 3 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.

5. An improvement as defined in claim 2 wherein said first and second portions of said cross over conductors converge toward said recess.

6. An improvement as defined in claim 5 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.

7. An improvement as defined in claim 6 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.

8. An improvement as defined in claim 1 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.

9. An improvement as defined in claim 8 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.

10. An improvement as defined in claim 1 wherein said first and second portions of said cross over conductors converge toward said recess.

11. An improvement as defined in claim 1 wherein said parallel conductor includes first and second axially spaced sections, said first sections being spaced from said one cross over conductor and being spaced a given distance from said cylindrical body and said second sections extending from said first sections to said one cross over conductor, said second sections being tapered away from said cylindrical body in a direction from said first sections toward said first cross over conductor.

12. An improvement as defined in claim 11 wherein said layer is spaced from said cylindrical body approximately said given distance. 

1. In an inductor for inductively heating an elongated workpiece as it is rotated about a central axis; said workpiece including a generally cylindrical shaft portion concentric with said axis, a flange including a surface generally orthogonal to said axis and facing said shaft portion and a circumferentially extending recess between said shaft portion and said flange surface, said recess extending axially inwardly of said surface in a direction opposite to said shaft portion; said inductor including two generally parallel conductors extending along said shaft portion and into said recess and first and second cross over conductors joining said parallel conductors at axially spaced positions along said shaft portion with the first of said cross over conductors extending into said recess, said conductors being spaced from and inductively coupled to said workpiece, tHe improvement comprising: said one cross over conductor having a first portion generally facing said shaft portion of said workpiece, a second portion facing away from said shaft portion and a third portion between said first and second portions and generally facing into said recess; and a layer of high permeability material between said first portion and said shaft portion, said layer being carried by said first portion, spaced from said shaft portion and having a thickness allowing saturation thereof when an alternating induction heating current is passed through said inductor.
 2. An improvement as defined in claim 1 wherein said first portion is spaced from said shaft portion a given distance and said thickness is at least one half of said distance.
 3. An improvement as defined in claim 2 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.
 4. An improvement as defined in claim 3 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.
 5. An improvement as defined in claim 2 wherein said first and second portions of said cross over conductors converge toward said recess.
 6. An improvement as defined in claim 5 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.
 7. An improvement as defined in claim 6 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.
 8. An improvement as defined in claim 1 including a second layer of high permeability material secured onto said second portion of said one cross over conductor.
 9. An improvement as defined in claim 8 including an element of high permeability material joining said first mentioned layer and said second layer, said element being in engagement with said one cross over conductor at a position opposite to said third portion and said recess.
 10. An improvement as defined in claim 1 wherein said first and second portions of said cross over conductors converge toward said recess.
 11. An improvement as defined in claim 1 wherein said parallel conductor includes first and second axially spaced sections, said first sections being spaced from said one cross over conductor and being spaced a given distance from said cylindrical body and said second sections extending from said first sections to said one cross over conductor, said second sections being tapered away from said cylindrical body in a direction from said first sections toward said first cross over conductor.
 12. An improvement as defined in claim 11 wherein said layer is spaced from said cylindrical body approximately said given distance. 